1. Field of the Invention
This invention relates to blends of ethylene copolymers, curable compositions, and shaped articles formed therefrom. More particularly this invention relates to blends of thermosetting resins with copolymers of ethylene, a flexibilizing monomer, a third monomer which contains epoxy side groups, and optionally carbon monoxide. This invention also relates to shaped articles, films, and fibers formed from such blends.
2. Description of the Prior Art
Ethylene polymers are characterized by a low polarity and low reactivity. They are like waxes in this respect, having a low dielectric constant and being soluble in hot oils, hot wax and hot hydrocarbons. They also are well known to be very inert. For some uses it is desirable to modify the ethylene polymers to make them flexible, to impart more polarity to the polymers, and to be able to use them in reaction with other resins. A small degree of polarity and a certain amount of flexibility can be imparted to an ethylene polymer by incorporation therein of unsaturated organic esters, such as vinyl acetate or acrylates. However, to obtain a high degree of polarity high levels of ester are required which in turn adversely affects the inherit advantage of the long ethylene chain, e.g., low cost, good low temperature behavior, etc. Thus it is desirable to increase the polarity of an ethylene copolymer while retaining the hydrocarbon chain as the major feature of the polymer. Ethylene copolymers, however, modified to be more flexible and more polar may still be relatively unreactive.
The art regarding thermosetting resins and especially blends with other polymers will now be considered. Commercially available thermosetting resins such as phenolics, epoxys, etc., have been found to be useful because of the retention of their performance at elevated temperatures. This retention of performance is associated with the cross-linking or curing action inherent in the structure of the thermosetting resins utilized. However, this retention of high temperature performance is accompanied by high stiffness and brittleness making it desirable to lower the stiffness of such material or if some stiffness is desired by providing a higher degree of toughness. The obvious solution, to blend a flexible polymer into the thermosetting resin, has not been successful to the best of our knowledge. Molecular compatibility has not been achieved; the desirable properties of the thermoset are lost.